Whale Trail, the colourful iPhone and iPad game that sees you chasing bubbles through the sky with a whale, is about to get a free version in the next couple of weeks, the developers behind the game have confirmed to Pocket-lint.

Although there can't be many that can complain about the 69p price for the highly addictive game, that isn't stopping ustwo, the developers, creating a free version to woo gamers.

In an interview with Pocket-lint, Mills the co-founder of ustwo, told us that the focus of the new version would be about earning "krill" to customise and improve your whale, called Willow.

"There will be treats, costumes, wallpapers, and the ability to enhance your whale," explains Mills.

Users will be able to earn krill by completing levels, which they can then spend on the above just like coins and bucks in games such as Draw Something or Tiny Tower.

As you might expect, users will be able to buy more Krill if they can't wait to collect enough gaming credit by actually gaming - 4,000 krill will cost 69p, for example.

The new free version of the app is expected to land in the Android and Apple app stores shortly.

Mills confirmed to Pocket-lint that the original paid for version would no longer be available.

"People who have already downloaded the game [when it was 69p] will get a big bag of krill to spend in the shop to say thanks for previously having bought it," added Mills.